As is well known in the art, most reactions generated in an oil refining process are exothermic reactions. Generally, a quenching zone is formed between catalytic layers to remove heat generated by the exothermic reactions. In the quenching zone, high-pressure gas or liquid descending from the upper catalytic layer is mixed with quenching fluid which is injected into the quenching zone, thus cooling beneath a predetermined temperature.
Typically, the quenching zone includes a quenching box and a mixing box. In the quenching box, a quenching ring or a quenching pipe ejects quenching fluid to gas or liquid descending from the upper catalytic layer, thus primarily mixing the quenching fluid with the gas or liquid, thereby cooling the gas or liquid.
To further enhance the quenching efficiency, the quenching fluid and the gas or liquid flow into the mixing box and then are secondarily mixed with each other in the mixing box. The recent trend of the structure of the quenching zone is to keep the quenching fluid in the quenching zone for a longer residense time so as to increase the duration that the quenching fluid makes contact with the gas or liquid. To realize this, a mechanical mechanism for creating swirls has been used.
Representative examples of conventional mixing apparatuses used in quenching zones were proposed in U.S. Pat. No. 3,353,924, No. 3,541,000, No. 4,669,890 and No. 5,152,967. However, some of these apparatuses are complicated and are thus prone to plugging. In addition, some need a relatively large space to provide a satisfactory degree of mixing. Furthermore, some induce a large drop in pressure and thus cannot be used.